Circuit breaker



Aug. 25, 1931. K. c. RANDALL CIRCUIT BREAKER Filed NO'v'I 27, 1929 2SheetsShee INVENTOR Karl 6. Eanaa/l ATTORNEY Patented Aug. 25, 1931UNITED STATES PATENT OFFICE KARL C. RANDALL, OF EDGEWOOD, PENNSYLVANIA,ASSIGNOR TO WESTINGHOUSE ELECTRIC & muraerunme COIPANY, A CORPORATION OFPENNSYLVANIA CIRCUIT BREAKER Application fled llovember 27, 1929. SerialNo. 410,113.

My invention relates to circuit breakers responsive portion of the tripmechanism may and particularly to enclosed oil-filled circuit breakershaving automatic tripping means for causing such circuit breakers toopen under predetermined current conditions.

Heretofore bushing or ring type current transformers could bepractically used in conjunction with trip coils to control high-tensioncircuit breakers only where the current values exceed certain limits andwere not practical for overload and short-circuit protection belowcircuit-breaker ratings of about fifty amperes. It was, therefore,necessary to employ other means for controlling high-tension circuitbreakers of relatively low current ratings. For this purpose,wound-primary type transformers are usually employed, but these have thedisadvantage of requiring relatively expensive insulations and occupyconsiderable space exterior of the circuit-breaker housing.

An object of my invention is to provide a control device forhigh-tension low-current circuit breakers wherein, a current transformerimmersed in oil within the circuitbreaker housing is employed toenergizea thermal elementthat is operative, on relatively low currents, fortripping the latch mechanism of the circuit breaker.

Another object of my invention is to probreaker when an objectionableoverload has endured for a predetermined time.

A further object of my invention is to provide a circuit breaker whereinthe trip mechanism may be energized by a relatively small to currentsupplied by a current transformer associated with one of thecircuit-breaker con- {5 characteristics wherein the trip mechanism maybe rotected against destructive forces induced y sudden overload orshort-circuit surges.

A further ob ect of my invention is, to pro- 60 vide a circuit breakerwherein the currentbe enclosed within the circuit-breaker housing andwhich is relatively compact and may be carried upon the bushing of thestationary contact or upon the moving contact.

A further object of my invention is to provide a circuit breaker havinga thermal-responsive trip mechanism that will be infiuenced by currentproportional to that flowing through the circuit-breaker contacts andwhich will not be responsive to changes in ambient temperature.

A further object of my invention is to pro vide a circuit breaker with atrip mechanism to be energized by a current transformer and wherein theusual expensive insulation may be dispensed with by placing thetransformer in the circuit-breaker housing and immersing it in the usualinsulating fluid within the housing.

These and other objects that will be made apparent throughout thefurther description of my invention are attained by means of theapparatus hereinafter described, and illustrated in the accompanyingdrawings, wherein Figure 1 is a vertical section through acircuitbreaker embodying features of my invention,

Fig. 2 is a vertical section, on an enlarged scale, showing a detail ofthe current-responsive trip mechanism shown in Fig. 1.

Fig. 3 is a transverse section through the device shown in Fig. 2, takenon the line IIIIII thereof,

F i 4 is a vertical section through a circuit breaker disclosing amodified form of the thermal-responsive trip mechanism, and

Fig. 5 is a wiring diagram of a modified control circuit.

Referring to the drawings and particularly to Fig. 1, thecircuit-breaker apparatus comprises a metal housing 8 containinginsulating fluid 9, such as oil, and provided with a metal cover 11 thatis fixed to the housing by means of bolts 12. The cover 11 supports apair of contact bushin s 13 which support stationary contacts 14 avingexteriorly projecting terminals 15 to which the feed conductors 16 areconnected.

The stationary contacts 14 are adapted to be connected by a movablebridging contact device 17 that is provided with an operating beingconnected by a conductive cable 21 that is connected to the terminals 22of the primary coil 23 of a wound-type transformer24. The transformer 24is mounted upon the in sulating bar and its purpose will hereinafterappear. 7 p

The nature of the contact between the stationarycontact jaws-14 and thecontact blades 19 of the bridging contact 17 is such that,

.when the rod 18 is released, the bridging contact 17 is caused to fallaway from the g -contacts 14 under the influence of gravitational force.a

The bridging contact device 17 is retained in closed position by meansof a latch bar 25 that engages a notch 26in the operating rod A urposebf my invention is to provide a simple and inexpensive means fortripping the circuit breaker to open position, inbresponse to anoverload condition, after an overload has persisted in the circuit apredetermined time.

Heretofore, high-tension low-current circult breakers have been openedby'trip-coil .devices energized-by transformers mounted exteriorly ofthe circuit breaker and requiring relatively expensive insulation. Inorder to reduce the cost of the-trip mechanism,

" through an opening 33 therein and is brought into operative relationto a toglgle link contype is mounted u a transformer 24 of a simplewound-primary within the circuit-breaker tank or casing.

order that the circuit breaker may be tr pped to open position underpredetermmed current conditions, I have provided a tri which projects,exteriorly of the cover 11 stituting a part of the trip mec anismheremafter described.

bracket that is mounted upon the cover 11 aiid'is actuated by abell-crank lever 35 pivotally mounted on the bracket. The lever 35 isloosely connected to a vertical trip rod *3fi slidably mounted in aguide 37, the rod being pivotedvto the knee pivot'38 of a pair to theends of the links 39 and41, serves 1 of toggle links 39 and 41 that aremovably mounted, by slot-and-pin connections 42,

l upon the. bracket" 34.

An over-center spring 43, that is connected to bias the knee .of thepivot toward either an upward position, as shown, or .adown-- wardposition into engagement with theiup 26 and to thereby retain the shaft18 in closed n the movable circuitbreaker contact which is immersed inthe oil rod 32, made of'insulating material, 7

32 is of such length that, when the bridging contact member 17 is inclosed position, the upper end thereof lies directly beneath theoverhanging portion of the toggle link 41, and a slight upward movementthereof will cause the knee pivot 38'0f the toggle to move below theabove-noted center line, at which time, the spring 43 will cause thetoggle to collapse downwardly until the knee thereof rests upon the endof the resetting pin .44. V

- The enlarged end of the release rod engages the horizontal arm of thebell-crank lever 35' and causes withdrawal of the latch 25 andsubsequent opening of the contact member; 17 which falls away from thestationary contacts 19. As the shaft 18 drops, the link 46 causes thetoggle to move resetting pin which resets the toggle. \Vhen the contactmember 17 is moved to closed position, the spring 47, connected to thelever 35 causes the latch to be moved into the notch ,(position. a

With particular reference to Figs. 1, 2 and 3, it will be seen that thetrip rod 32 is mounted upon a pair of flexible diaphragms 48 and 49 thatare supported by a "cylindrical casing 51 to serve to so seal the endsthereof that the liquidwithin the circuit breaker housing cannot enterwithin the casing 51, which is mounted upon the movable bridging contactmember 17.

Hbimetal element 52; of U-shape, and hav-' ing a pair of terminals'53and 54, is mounted in horizontal position within the casing 51,

the terminals 53 and 54 extending through an insulating bushing 55 inthe wall of the I f casing, as indicated in Figs. 2 and 3. The The latch25 1s shdably supported in a terminals are respectively connected to theterminalsof a secondary winding 56 of the transformer 24.' The currentinduced therein passes through the bimetal element 52 and issubstantially proportional to that flowing through the winding 23 andthe bridging contact device 17.

A second bimetal element 57 'is mounted ,upon the casing 51 andinteriorly thereof and .directly. opposite the bimetal element 52, as-

indicatedjnF 2 and 3. The bimetal element-52 1s so positioned' that thefree end thereof is deflected upwardly when heated to a predeterminedtemperature, while the .bimetal element 57 isso positioned that .a tisenected to the trip rod 32 by means of a yoke 58 pivotally mounteduponthe trip rod and having downwardly extending fingers 59 and 61 thatrespectively engage the bimetal elements 52 and 57. Since the rod 32 isconnected to the diaphragms '48 and 49, which have substantially equalexternal pressure thereon, the rod 32 is free to move in response bi;movement of the bimetal elements 52 and Since, ordinarily, the free endof the bimetal element 52 moves upwardly the same distance as the freeend of the bimetal element 57.moves downwardly in response to a rise inambient temperature, substantially no movement of the rod 32 will resultl'rom variations in the ambient temperature of the control mechanism.However, should an abnormal current flow through the circuit breaker andthe bridging contact device ill, a correspondingly increased currentwill flow through the bimetal element 52 which is connected to thesecondary transformer winding 56.

At such time, the free end of the bimetal element 52 will move upwardlwhile the free end of the bimetal element 5 remains practicallystationary, causing a suflicient upward movement of the rod 32 to tripthe toggle and thereb release the operating shaft 18 to permit t ecircuit-breaker contact device 17 to fall to open position.

The bimetal element 52, preferably, may have inverse timecharacteristics and may be calibrated to cause the circuit breaker toopen 1 when an overload of predetermined proporti'ons has endured for apredetermined time.

7 It will be noted that the current-responsive device is relativelysimple in construction and, because of its compact proportions may becarried conveniently upon the bridging contact and immersed in the fluidwithin the circuit-breaker tank. The control device, being thusenclosed, isprotected from contact with extraneous objects withoutrequiring special coverings, and tampering therewith is recluded.

urrent transformers for high-tension service, such as are usually emploed with high-tension low-current circuit reakers, are placed in separatetanks and require special, relatively expensive insulation and arerelatively large. By immersin the transformed in the insulatin fluidwithin the circuit-breaker housing, t e transformer parts may be reducedin size, and no special insulation is required. Consequently, the sizeand cost of the transformer may be materially reduced.

Referring to Fig. 4, a modified form of con trol mechanism for a circuitbreaker similar to that shown in Fig. 1, is illustrated. The tripmechanism, which is entirely immersed in the insulating fluid within thetank, is similar to that shown in Fig. 1, but the trans former andthermal device are mounted upon one of the insulating terminal bushings.

The advantage of this construction resides in the removal of all controlmechanism from the bridging contact device, thereby reducing the weightand the inertia of the movable contacts and permitting of high-speedoperation. Furthermore, all of the tripping mech- .anism is enclosedwithin the tank and immersed in the insulating fluid, thereby affordingcomplete protection to such mechanism.

The current transformer 24 for energizing terminal and the contact 14,respectively,

in such manner that all of the current assing through the circuitbreaker passes trough the primary winding. The operation of the circuitbreaker is substantially the same as that of the breaker shown'in Fig.1.

In Fig. 5, I have shown a means for protecting the bimetal elementagainst abnormal curthe bimetal element 52 is mounted upon the r rentsurges that would be injurious to it,

which comprises a reactor 66 for shunting the bimetal element. Undernormal operating conditions, the current is so divided that it flowsmainly through the bimetal element but, when a heavy surge is induced inthe secondary winding 56 of thetransformer, the core of the reactorbecomes saturated and permits the main portion of the current to passthrough the coil 67 of the reactor and thus d1- vert destructivecurrents from the bimetal element.

While I have illustrated several embodiments of my invention, it will beapparent to those skilled in the art that various changes,modifications, substitutions, additions and omissions may be made in theapparatus illustrated without departing. from the spirit and scope of myinvention, as set forth in the appended claims.

' claim as my invention:

1. The combination with anenclosed circuit breaker having a casing, amovable contact member within the case and a means carried by the casingfor. releasably retaining the said member in closed position, of acurrent-responsive means for actuating the releasing means in responseto predetermined current conditions, carried by the movable contactmember, and so movable thereby, that it is placed in operative relationto the said releasing means when the contact member is in closedposition.

2. The combination with a circuit breaker having a movable contactmember and a means for releasably retaining said member in closedposition, of a current-responsive member carried upon said member andoperated by current induced by that passing through the contact memberfor actuating the retaining means.

3. The combination with a circuit breaker havlng a pair of relativelymovable contact members and a means for releasably retaining the contactmembers in engaged position, of a current-responsive member carried uponone of said contact members and operated by current induced by thatpassing through one of the contact members for actuating the releasingmeans.

4. The combination with an enclosed circuit breaker having a movablecontact member immersed in liquid and a means for releasably retainingsaid contact member in closed position, of an enclosed current-re-'sponslve device mounted upon the lmmersed contact member and energizedby current "passing through the contact member for actuating theretaining means.

5. The combination with an enclosed circuit breaker having a movablecontact member and a releasing member mounted upon the enclosure forreleasably retaining the a transformer within the tankand immersed inthe insulating fluidfor-energmmg the 52nd current-responsive means.

8. A circuit breaker comprising a tank containing insulating fluid, apair of relatively. movable contact members within the tank and immersedin the insulating fluid, means for releasably retaining the contactmembers in closed position, a current-responsive element immersed in theinsulating fluid for, releasing the retaining means, and a transformerwithin the tank for energizing the current-responsive means.

9. A circuit breaker comprlsing a tank containing insulating fluid, apair of relatively.

movable contact members within the tank and immersed in the insulatingfluid, means for releasably retaining the contact members in closedposition, a current-responsive element immersed in the insulating fluidfor releasably retaining the contact members in 95 closed position, acurrent-responsive element for releasing the retainin means; and'atransformer within the tan for energizing the said current-responsivemeans.

In testimony whereof, I have hereunto subscribed my name this 21st dayof November, 1929. KARLC. RANDALL.

contact member in closed position, of a current-responsive membercarried upon the movable contact member and movable therewith intooperative relation to the releasing member when the contact member ismoved to closed position.

6. A circuit breaker comprising a housing having a cover, a contactfixed to'the cover,

' a movable contact within the housing for engaging the first contact,means mounted on the cover for releasably retainin the movable contactin closed position, an a currentresponsive means for actuating thereleasing means and carried upon the movable contact and operative]associated with the releasing means only w 1811 the movable contact isin closed position.

7. A circuit breaker comprising a tank containing insulating fluid, apair of relatively movable contact" members within the tank and'immersedin the insulating fluid, means for releasably retaining the contactmembers in closed position, a current-responsive elen5- ment forreleasing the retaining means, and

